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Python 爬虫项目示例

2017-11-28 23:59 316 查看


创建 python 爬虫项目，从上图左至右，创建5个类：

主类：SpiderMain

URL管理类：UrlManager

网页下载类：HtmlDownloader

网页解析类：HtmlParser

输出类：HtmlOutputer



主类：SpiderMain

# coding:utf8

from baike_spider import url_manager, html_downloader, html_parser,html_outputer

class SpiderMain(object):
def __init__(self):
self.urls = url_manager.UrlManager()
self.downloader = html_downloader.HtmlDownloader()
self.parser = html_parser.HtmlParser()
self.outputer = html_outputer.HtmlOutputer()

def craw(self, root_url):
count = 1
self.urls.add_new_url(root_url)
while self.urls.has_new_url():
try:
new_url = self.urls.get_new_url()
print("craw %d : %s" %(count, new_url))
html_cont = self.downloader.download(new_url)
new_url, new_data = self.parser.parse(new_url, html_cont)
self.urls.add_new_urls(new_url)
self.outputer.collect_data(new_data)
if count == 1000:
break
count = count + 1
except:
print("craw failed")

self.outputer.output_html()

if __name__=="__main__":
root_url = "https://baike.baidu.com/item/Python/407313"
obj_spider = SpiderMain()
obj_spider.craw(root_url)

URL管理类：UrlManager
# coding:utf8

class UrlManager(object):
def __init__(self):
self.new_urls = set() #待爬取url集合
self.old_urls = set() #已爬取url集合

def add_new_url(self,url):
if url is None:
return
if url not in self.new_urls and url not in self.old_urls:
self.new_urls.add(url)

def add_new_urls(self,urls):
if urls is None or len(urls) == 0:
return
for url in urls:
self.add_new_url(url)

def has_new_url(self):
return len(self.new_urls) != 0

def get_new_url(self):
new_url = self.new_urls.pop()
self.old_urls.add(new_url)
return new_url

网页下载类：HtmlDownloader
# coding:utf8
import urllib.request

class HtmlDownloader(object):

def download(self,url):
if url is None:
return None

response = urllib.request.urlopen(url)

if response.getcode() != 200:
return None

return response.read()

网页解析类：HtmlParser
# coding:utf8
import re
from bs4 import BeautifulSoup
import urllib.parse as urlparse

class HtmlParser(object):

def _get_new_urls(self, page_url, soup):
new_urls = set()
# /item/%E9%9B%86%E6%88%90%E5%BC%80%E5%8F%91%E7%8E%AF%E5%A2%83
links = soup.find_all('a',href=re.compile(r"/item/.*"))
for link in links:
new_url = link['href']
new_full_url = urlparse.urljoin(page_url,new_url)
new_urls.add(new_full_url)
return new_urls

def _get_new_date(self, page_url, soup):
res_data = {}
#url
res_data['url'] = page_url
#<dd class="lemmaWgt-lemmaTitle-title"><h1>Python</h1>
title_node = soup.find('dd' ,class_="lemmaWgt-lemmaTitle-title").find('h1')
res_data['title'] = title_node.get_text()
#<div class="lemma-summary" label-module="lemmaSummary">
summary_node = soup.find('div' ,class_="lemma-summary")
res_data['summary'] = summary_node.get_text()
return res_data

def parse(self,page_url,html_cout):
if page_url is None or html_cout is None:
return
soup = BeautifulSoup(html_cout,'html.parser')
new_urls = self._get_new_urls(page_url,soup) #当前页面的所有网址
new_data = self._get_new_date(page_url,soup) #当前页面的 title、summary
return new_urls, new_data

输出类：HtmlOutputer
# coding:utf8

class HtmlOutputer(object):
def __init__(self):
self.datas = []

def collect_data(self,data):
if data is None:
return
self.datas.append(data)

def output_html(self):
fout = open('output.html','w')
fout.write("<html>")
fout.write("<body>")
fout.write("<table>")
for data in self.datas:
fout.write("<tr>")
fout.write("<td>%s</td>" % data['url'])
fout.write("<td>%s</td>" % data['title'].encode('utf-8'))
fout.write("<td>%s</td>" % data['summary'].encode('utf-8'))
fout.write("</tr>")
fout.write("</table>")
fout.write("</body>")
fout.write("</html>")


原视频教程：Python开发简单爬虫
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